Multimode wireless terminals equipped with a plurality of interfaces of different wireless systems such as interfaces for wireless LAN (Local Area Network) conforming to IEEE (the Institute of Electrical and Electronics Engineers, Inc.) 802.11, in addition to interfaces for cellular networks such as 3GPP (Third Generation Partnership Project) and LTE (Long Term Evolution), have been known. Multimode wireless terminals improve user-friendliness by automatically selecting appropriate wireless systems according to shifts in location. For examples, a cellular interface covering a wider area is used outdoors, while a non-chargeable wireless LAN is used indoors.
Further, regarding a wireless LAN of IEEE 802.11a using a 5 GHz band for example, as outdoor use is regulated by the law, wireless modes which can be used indoors and outdoors may be different. As such, automatic switching to a wireless communication mode which is compliant with the regulation, in accordance with shifts in location, leads to an improvement in user-friendliness.
Further, for a user who uses the same wireless communication equipment at home and at the office, manually changing the setting of the wireless communication equipment each time the user moves between home and the office is troublesome. As such, it is desirable that the wireless communication equipment determines whether it is at home or at the office by itself so as to be able to automatically select the wireless mode without being set by the user.    Patent Document 1: JP 2003-283509 A    Patent Document 2: JP 2002-107443 A    Patent Document 3: JP 2005-123662 A    Patent Document 4: JP 06-093650 B
As a means for determining the position of a terminal, a system using GPS (Global Positioning System) is typical. However, as it is difficult to capture GPS signals indoors, an accurate position of a wireless communication terminal placed indoors is difficult to identify. While it may be possible to estimate the indoor position using an acceleration sensor or presume whether or not it is located indoors using an optical sensor, providing these sensors to a wireless communication terminal would lead to an increase in the manufacturing cost and an increase in volume of the terminal. As such, such sensors are less likely to be provided to a small and low-priced wireless communication terminal.
Patent Document 1 discloses a method using a six-directional antenna. In this method, whether or not there is a roof or a wall is determined based on a signal reflection time, whereby it is determined whether the wireless communication terminal is indoors or outdoors. However, if both home and the office are in the doors, there is a problem that this method cannot distinguish whether the wireless communication terminal is at home or at the office. Further, as heights of roofs and positions of walls differ one another and any conditions can be expected, there is a problem that the above method is not able to accurately determine whether a wireless communication terminal is indoors.
Patent Document 2 discloses a method of estimating the position of a wireless communication terminal using a survey system. In this method, a wireless communication terminal, which is a target of position estimation, must be positioned within a communication area of a plurality of base stations, and further, the target wireless communication terminal needs to know the positions of those base stations. Further, as this method is a method of surveying a received signal strength indicator (RSSI) measured by a wireless device, it is easily affected by the surrounding environment, leading to a problem of low reliability in the measurement result.
Patent Documents 3 and 4 disclose art of preliminary storing a received field value at a specific position from each base station, and specifying the position of a wireless communication terminal based on the stored received field value and a received field value received by the wireless communication terminal. Even in this case, it is necessary to preliminary store a plurality of received field values, that is, values from at least three base stations, for each location.
In view of the above, the above-described art needs to previously measure received field strengths with respect to a plurality of base stations in order to specify the position of a wireless communication terminal, which needs an extensive configuration and causes a problem of cost increase. Further, because base stations are used, parameters which can be used for specifying the position of a wireless communication terminal are limited to received field values. This also causes a problem of low reliability in the measurement result due to an influence of the surrounding environment.